1. Field of the Invention
The present invention relates to a control device for "plunger needles" in crochet galloon machines, of the type comprising: a needle bar oscillatably connected to the bed of a crochet galloon machine and fixedly engaging the rear ends of a plurality of needles disposed parallelly in side-by-side relation one following the other; at least a connecting rod for the needle control, the front end of which is operatively connected to the needle bar; a main shaft rotatably supported by the machine bed and carrying at least an eccentric for the needle control, operatively engaged to the rear end of the needle control connecting rod to impart the needles a reciprocating motion in the longitudinal direction; a thrust bar oscillatably connected to the machine bed and engaging the rear ends of a plurality of closure latches each slidably guided over one of said needles; a driving mechanism for the control of the closure latches which is operated by the main shaft and acts upon the thrust bar to impart a reciprocating motion in the longitudinal direction to the closure latches in synchronism with the needle movements.
2. Prior Art
It is known that there are crochet galloon machines provided with the so-called "plunger needles" which, slidably supported by a front grooved bar in side-by-side relation, cooperate with other members, such as for example eye-pointed needles for the warp yarns and tubular guides for the weft yarns, to produce a manufactured article by interlacing weft yarns with warp yarns.
Plunger needles consist each of two separate portions. In greater detail, each plunger needle comprises a true needle, exhibiting a hook-shaped front end projecting in cantilevered fashion from the front grooved bar, and a so-called closure latch, also referred to as "plunger" by those skilled in the art, which appears in an overlaid position with respect to the needle and is guided lengthwise over the same.
When the needles fixedly carried by a needle bar are being operated, they receive a reciprocating motion in a substantially longitudinal direction. Meanwhile the closure latches, carried by a so-called thrust bar, are reciprocated in a longitudinal direction too in synchronism with the needle movements. In greater detail, the movement of the closure latches enables each of them to be moved relative to the needle from a closure condition in which the front end of the latch closes the round bend formed by the hooked end of the needle, to an opened condition in which the latch is disposed in a backward position on the needle to open the yarn passage to said round bend.
The synchronized operation of the needles and closure latches takes place by means of suitable control devices receiving the movement from cams and/or eccentrics carried by a main shaft driven in rotation.
In greater detail, in the known control devices the needle bar and thrust bar are provided to be mutually superposed and fastened, each by its respective opposite ends, to a pair of rods slidably guided with respect to the machine bed. Connected to each rod is a pair of rollers acting by contact, on diametrically opposite sides, upon the profile of a respective cam carried by a main shaft operable in rotation. The cam is so shaped that by acting on the respective rollers it causes both the going and return strokes of the corresponding needle bar or thrust bar.
While the devices of this type have proved to be satisfactory in operation, it has been ascertained that above all when high speeds are concerned, the big masses involved can easily give rise to an early wear of the cam followers and/or profiles as a result of a prolonged use of the machine.
In addition these devices do not allow an easy adaptability of the crochet galloon machine to the execution of workings of different types. It is to be pointed out in the connection that, in operation, the closure latches must carry out temporary stops when they reverse their reciprocating motion. These temporary stops need to be more or less long depending upon the type of working which is being performed. Since the movements of the latches are directly correlated to the cam profile controlling the movements of the thrust bar, it results that it is necessary to replace the cam when the device must carry out a working different from the preceding one. This requirement gives rise to problems not only as regards the time necessary for replacing the cam but also because different types of cams adapted to perform the different workings need to be kept in stock.